Yes, it lacks this, because all objects created by Primitives (except for the plane) are lathe objects. You can't scale these objects in three dimension due to the way they are created. If you want to create the box in code and not in an editor, take this code and modify it, so that dimensions in x/y/z directions actually differ:
Object3D box=new Object3D(12);
SimpleVector upperLeftFront=new SimpleVector(-1,-1,-1);
SimpleVector upperRightFront=new SimpleVector(1,-1,-1);
SimpleVector lowerLeftFront=new SimpleVector(-1,1,-1);
SimpleVector lowerRightFront=new SimpleVector(1,1,-1);
SimpleVector upperLeftBack = new SimpleVector( -1, -1, 1);
SimpleVector upperRightBack = new SimpleVector(1, -1, 1);
SimpleVector lowerLeftBack = new SimpleVector( -1, 1, 1);
SimpleVector lowerRightBack = new SimpleVector(1, 1, 1);
// Front
box.addTriangle(upperLeftFront,0,0, lowerLeftFront,0,1, upperRightFront,1,0);
box.addTriangle(upperRightFront,1,0, lowerLeftFront,0,1, lowerRightFront,1,1);
// Back
box.addTriangle(upperLeftBack,0,0, upperRightBack,1,0, lowerLeftBack,0,1);
box.addTriangle(upperRightBack,1,0, lowerRightBack,1,1, lowerLeftBack,0,1);
// Upper
box.addTriangle(upperLeftBack,0,0, upperLeftFront,0,1, upperRightBack,1,0);
box.addTriangle(upperRightBack,1,0, upperLeftFront,0,1, upperRightFront,1,1);
// Lower
box.addTriangle(lowerLeftBack,0,0, lowerRightBack,1,0, lowerLeftFront,0,1);
box.addTriangle(lowerRightBack,1,0, lowerRightFront,1,1, lowerLeftFront,0,1);
// Left
box.addTriangle(upperLeftFront,0,0, upperLeftBack,1,0, lowerLeftFront,0,1);
box.addTriangle(upperLeftBack,1,0, lowerLeftBack,1,1, lowerLeftFront,0,1);
// Right
box.addTriangle(upperRightFront,0,0, lowerRightFront,0,1, upperRightBack,1,0);
box.addTriangle(upperRightBack,1,0, lowerRightFront, 0,1, lowerRightBack,1,1);
box.setTexture("base");